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Pra- trial chemistry form 5 – MRSM PC – 2012- dated july 2012

SECTION A: OBJECTIVE

1. Which of the following shows the correct type of particles for each substance?

Atom Molecule IonA Water Magnesium Sodium ChlorideB Magnesium Carbon dioxide Sodium ChlorideC Sodium Chloride Carbon dioxide MagnesiumD Magnesium Sodium Chloride Carbon dioxide

2. Substance T exists as liquid at temperature of 120 oC. Which of the probable melting point of substance T?

Melting point /oC Boiling point /oCA 2 62B -41 21C 140 190D 75 130

3. Which of the following is a use of carbon-14?

A. to treat cancer patientsB. To estimate the age of fossils and artifactsC. To study the metabolism of phosphorus in plantsD. To destroy bacteria in food without changing the quality of the food.

4. Diagram 1 is a graph of temperature – time for heating of substance Q

Which statement is correct about the property of substance Q based on the graph?

A. Is a gas at room temperatureB. physical state start changes at temperature 75oCC. Releases heat at time interval t1 and t2D. Only in liquid condition at time interval t1 and t2 oC

Temperature(oC)

Time (s)

Diagram 1

75

t 1 t 2

2

5.The following equation represents a reaction What are the reactants in this equation?

. Cu(OH)2(s) + 2HNO3(aq) Cu(NO3)2(aq) + 2H2O(1)

A Copper(II) nitrate and water B Copper(II) nitrate and nitric acid C Copper(II) hydroxide and nitric acid D Copper(II) hydroxide and copper(II) nitrate

6. Which of the following is not a chemical property of acids?A Reacts with carbonate to produce salt, water and carbon dioxideB Reacts with reactive metal to produce salt and hydrogenC Reacts with metal oxide to produce salt and waterD Reacts with alkali to produce salt and hydrogen

7. The following equation represents the neutralisation reaction between barium hydroxide, Ba(OH)2 and hydrochloric acid, HCl.

Ba(OH)2 + 2HC1 BaCl2 + 2 H2O

What is the volume of 0.5 mol dm hydrochloric acid needed to neutralise 25 cm3 of 0.1 mol dm-3 barium hydroxide?

A 2.5 cm3 B 5.0 cm3

C 10.0cm3 D 12.5cm3

8. Which of the following substances ionise completely in water?I Ammonia II Nitric acid III Ethanoic acidIV Sodium hydroxide

A I and II B I and IIIC II and IVD III and IV

9. Some transition elements and their compounds are useful catalysts in industries. Which pair is correct?

Catalyst Use in industry

A Iron Manufacture of nitric acid from ammonia

B Nickel Manufacture of ammonia

C Manganese(IV) oxide Manufacture of margarine

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D Ferum Manufacture of ammonia

10. Which pair is matched correctly?

Alloy Major component

A Brass Copper

B Pewter Zinc

C Bronze Tin

D Steel Carbon

11. Ammonium sulphate is used as a fertiliser.What is the percentage by mass of nitrogen in ammonium sulphate?[Relative atomic mass: H = 1; N = 14 ; O = 16; S = 32]A 10.6% B 12.3%

C 13.3% D 21.2%

12. Which substance is a natural polymer?

A Polythene B Polypropene

C Polyisoprene D Polyvinyl chloride

13. Which factor does not affect the rate of reaction?

A. Size of the solid reactantB. Volume of the reactantC. Concentration of the reactantD. Temperature of the reactant

14.Which of the following is the correct match of a low rate of reaction and a high rate of reaction?

Low rate of reaction High rate of reactionA. Neutralisation between hydrochloric acid and sodium

hydroxide solutionIron rusting

B. Double decomposition between lead (II) nitrate solution and potassium iodide solution

Neutralisation between hydrochloric acid and sodium hydroxide solution

C. Iron rusting Fermentation of glucose solutionD. Fermentation of glucose solution Double decomposition between

lead (II) nitrate solution and potassium iodide solution

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15. Which of the following reactants produces the highest rate of reaction with zinc powder?

A. 25 cm3 of sulphuric acid 0.1 moldm-3

B. 25 cm3 of ethanoic acid acid 0.1 moldm-3

C. 25 cm3 of nitric acid 0.1 moldm-3

D. 25 cm3 of hydrochloric acid 0.1 moldm-3

16. An experiment is carried out to determine the rate of reaction between sodium thiosulphate and hydrochloric acid. Which of the following combinations of conditions take the shortest time for the X mark to disappear from sight?

Sulphuric acid Sodium thiosulphate solutionTemperature / 0CVolume/ cm3 Concentration/

moldm-3Volume/ cm3 Concentration/

moldm-3

A 10 1.0 50 0.5 30

B 10 1.0 50 0.5 40

C 10 0.5 50 0.5 30

D 20 0.5 40 0.5 40

A Improving the tasteB Adding nutritional valueC Keeping the food tasterD Ensuring nutritional balance

17. Which of the following is not a function of food additives?

18. which substance is used as a food preservative?

A Sodium nitriteB Azo compoundC Ascorbic acidD Monosodium glutamate

19. which substances is commonly used to manufacture dyes and detergent?

A Sulphuric acidB Sodium chlorideC Phosphoric acidD Ammonium chloride

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20. A patient complained of a pain due to an excess of acid in the stomach. Which of the following substances will help to relieve the pain?

A AmmoniaB Ethanoic acidC Sodium chlorideD Magnesium hydroxide

SECTIONB : STRUCTURE

1. Diagram below shows the standard representation for the atoms of two elements, magnesium and chlorine.

a. What is represented by the number 24 in ?

_________________________________________________________ [1 mark]

b. i) Compare the size of the magnesium atom with the chlorine atom.

_________________________________________________________ [1 mark]

ii) Give a reason for your answer in b. i) above

_________________________________________________________

_________________________________________________________ [ 2 mark]

c. Complete Table 1 to show the position of chlorine in the Periodic Table.Element Period Group

Mg 3 2Cl

[1 mark]d. Magnesium reacts with chlorine to form a compound, magnesium chloride.

i) Write the formulae of ions in magnesium chloride.

________________________________________________________[1 mark]

ii) Draw the electron arrangement of the compound formed.[2 marks]

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iii) State two physical properties of magnesium chloride. _________________________________________________________

_________________________________________________________[2 marks]

TOTAL =10M

2) Diagram 2 shows the apparatus set-up to study the electrolysis of copper(II) sulphate solution . In Set I, carbon electrodes are used. In Set II, copper electrodes are used.

Diagram 2

(a) State all the anions and cations in copper(Il) sulphate solution.

Anion:

……………………………………………………………………………Cations:

…………………………………………………………………………..[2m]

(b) Based on Set 1 in Diagram 2:(i) Write the formula of the ion that is selectively discharged at the

cathode.

…………………………………………………………………………[l m]

(ii) State reason for your answer in (b) (i) above

……………………………………………………………………. [ 1m]

(iii) Write the half-equation for the reaction that takes place at the cathode.

coppercarbon

Set I Set II

Copper(II) sulphate solution

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……………………………………………………………………[2 m]

(iii) State the observation at the cathode.

…………………………………………………………………………[1 m]

(c) Based on Set 2 in Diagram 2:

(i) Name the product formed at anode

…………………………………………………………………………... [1m]

(d) Compare the intensity of blue colour of the copper(Il) sulphate solutions in Set I and Set II after one hour of electrolysis.Give one reason for the answer.

Comparison:

...............................................................................................................................

...............................................................................................................................

Reason:

…………………………………………………………………………………

…………………………………………………………………………………[2 m]

Total =10m

3 . Diagram 3 below shows laboratory activities in preparation of a salt.

Diagram 3

(a) Is the preparation of salt above for soluble salt or insoluble salt?

heat

Excess zinc oxide powder

heat

50 cm3 2 .0 mol/dm3 nitric acid

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…………………..……………………………………………………………… [1 mark]

(b) Explain why zinc oxide powder is added in excess.

………………..………………………………………………………………………… [1 mark]

(c) Write a chemical equation for the reaction that occurs inside the beaker.

…………………..……………………………………………………………………… [1 mark]

(d) Draw the apparatus set-up used to separate the excess zinc oxide powder from the mixture in the box in diagram 3 above.

[2 marks]

(e) name the salt formed

…………………………………………………………………………………………….[1 mark]

(f)Calculate the maximum mass of the salt formed. in ( e )

[Relative atomic mass: N=14, O=16, Zn=65] [3 marks]

(g) Suggest one substances that can replace zinc oxide in the experiment to obtain the same type of salt.

………………….………………………………………………………………………………………… [1 marks] Total = 10 m

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4. Table below shows the heat of neutralisation of two different monoprotic acids, P and Q with sodium hydroxide solution.

Experiment Reactants Heat of neutralisation/ kJmol-1

I 100cm3 1.0 moldm-3 sodium hydroxide solution +

100cm3 1.0 moldm-3 of monoprotic acid P-55.0

II 100cm3 1.0 moldm-3 sodium hydroxide solution +

100cm3 1.0 moldm-3 of monoprotic acid Q-57.0

a) What is the meaning of heat of neutralisation?

___________________________________________________________________________

___________________________________________________________________________[1 mark]

b) State one example which could be acid P and acid Q

P - ____________________________________________________

Q - ____________________________________________________ [2 marks]

c) Calculate the change in temperature of the mixture in experiment I[Specific heat capacity of solution: 4.2 Jg-1C-1]

[3 marks]d) i) Compare the value of heat neutralisation in experiment I and II

_________________________________________________________________________ [1

mark]ii) Briefly explain your answer in d(i)

_________________________________________________________________________

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_________________________________________________________________________ [2

marks]e) Draw the energy level diagram for reaction in experiment II

[2 marks] Total marks = 11

Max mark=10m

(5) Table 5 shows the molecular formulae and boiling points for three compounds, which are members of a homologous series.

Compound Molecular formula Boiling point ( 0C)P C2H4 -103Q C3H6 -48R C4H8 -6

Table 5

(a) (i) Name the homologous series for these compounds.

……………………………………………………………………………………………………………………………………….. [ 1 mark]

(ii) Write the general formula for this homologous series.

……………………………………………………………………………………………………………………………………..[ 1 mark]

(b) Explain why the boiling point for the members of this homologous series increase when the number of carbon atoms per molecule increases.

……………………………………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………………………………….. [ 3 marks]

( c) Write the chemical equation when compound P reacts with steam in the presence of phosphoric acid at temperature of 300 0C at 60 atm pressure.

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……………………………………………………………………………………………………………………………………………………

[ 2 marks]

( d) Compound P undergoes polymerisation. The structural formula for compound P is given below.

Write the equation for the polymerisation of compound P.

…………………………………………………………………………………………………………………………………… [ 2 marks]

(e) Draw the structural formula for Q.

[ 1 mark]

Total= 10m

6. Diagram 6 shows the apparatus set-up for an experiment to investigate electron transferat a distance in redox reactions.

Diagram 6

(a) State the colour of acidified potassium dichromate(VI) solution.

………………………………………………………………………………..[l m](b) When the circuit is completed, the galvanometer shows a deflection.

(i) Write the half-equation for the reaction at X.

Potassium iodide solution Acidified potassium dichromate(VI) solution

Sodium sulphate solution

Carbon

X

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………………………………………………………………………[l m](ii) State the type of reaction in 6(b)(i).

………………………………………………………………….……[l m]

(iii) Describe briefly a chemical test to identify the product formed in 6(b)(i).

………………………………………………………………………………

………………………………………………………………………………

……………………………………………………………………………… [2marks]

(c) (i) The half-equation below shows the reaction that occurs in acidified potassium dichromate(Vl) solution. Complete the half-equation.

Cr2O72- + …….. H+ + …….. e → ….. Cr3+ + ……. H2O

[2m](ii) Based on the answers in 6(b)(i) and 6(c)(i), on Diagram 6, draw the arrows

to show the direction of electron flow. [1m]

(d ) State the function of sodium sulphate solution

………………………………………………………………………………………………[1m]

(e) name the substance that can replace potassium iodide solution as the redox reaction occurs………………………………………………………………………………………………

[1m]

Total mark=10m

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Paper 37. A student carried out an experiment to investigate the rate of reaction between 5 g of large marble chips and crushed marble chips with 50 cm3 hydrochloric acid 1.0 mol dm-3 . Table 7 shows the data obtained from the experiment.Time (s)

Set 1Hydrochloric acid and 5.0 g large marble chips

Set 2Hydrochloric acid and 5.0 g crushed marble chips

Burette reading (cm3)

Volume of gas evolved (cm3)

Burette reading (cm3)

Volume of gas evolved (cm3)

0 50.00 0.00 50.00 0.0030 38.00 12.00 36.00 14.0060 30.50 19.50 29.50 20.5090120 22.00 28.00 19.00 31.00150 19.50 30.50 18.00 32.00180 18.50 31.50 18.00 32.00210 18.00 32.00 18.00 32.00240 18.00 32.00 18.00 32.00

Table 7 Diagram 7 shows the burette reading at 90 seconds for set 1 and set 2.

Diagram 7a) Based on Diagram 7, record the burette readings and volume of gas evolved at 90

seconds for both set in Table 7. [3 marks]

b) Based on Table 7, state how the volume of gas evolved changes when the marble chips react with hydrochloric acid in Set 1.

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______________________________________________________________

______________________________________________________________ [3 marks]

c) Based on this experiment, state the:

i. Manipulated variable :___________________________________

ii. Responding variable :___________________________________

iii. Constant variable :___________________________________[3 marks]

d) State the operational definition for the rate of reaction.

______________________________________________________________

______________________________________________________________ [3 marks]

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SECTION C; ESSAY

8(a) Diagram 8 shows the apparatus and observations for a redox reaction between iron(III) chloride solution and a metal.

At the beginning of the experiment After 30 minutes

Diagram 8

Based on the observations shown in Diagram 9, suggest a suitable metal to be used in this experiment.

Predict the ion present in the green solution and explain the answer based on the following aspects:

• The change in oxidation number for both the reactants

• The type of reaction that has occurred to each reactant

• The role of each reactant in the redox reaction

• The half-equations involved in the redox reaction

[10 marks]

……………………………….END OF QUESTION PAPER………………………………

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Answer scheme pra-trial 2012

Objective answer

1 B

2 D

3 B

4 B

5 C

6 D

7 C

8 C

9 D

10 A

11 D

12 C

13 B

14 D

15 A

16 B

17 D

18 A

17

19 A

20 D

STRUCTURED QUESTIONS

No Mark scheme Mark1a Nucleon number// atomic mass// total number of protons and

neutrons1

b) i

ii)

Chlorine atom is smaller than magnesium atom/(vice versa)

Proton number of chlorine is more than in magnesium Nuclei attraction in chlorine atom is more than in magnesium atom

1

11

c Period: 3Group: 17 1

d i Mg2+, Cl- 1 ii 1. Correct no of electrons in each shell

2. Correct charges and label nucleus11

iii High melting point/ boiling point Soluble in water/ insoluble in organic solvent White solid Conduct electricity in molten or aqueous solution

(any two)210

Answers Mark

2. (a) Anion : SO42- and OH-

Cation :Cu2+ and H+

(b) (i) Cu2+

(ii) The position of Cu2+ ion is lower than H+ ion in Electrochemical

Series

(iii) Half equation at cathode Cu2+ + 2e Cu

(iv) Brown solid is deposited

(c) Copper (ll) ion

(d) Comparison : The intensity of blue colour in Set 1 will decrease/fade

but in set 2 the intensity of blue colour remain

unchanged

1

1

1

1

2

1

1

1

18

Reasons : The concentration of Copper(ll) ions dereases in set 1 but

remain unchanged in set 2

1

Max : 10m

Suggested Answer mark3.a Soluble salt 1m b To ensure all the acid react completely 1m c ZnO + 2HNO3 Zn(NO3)2 + H2O 2m d

[functional apparatus] 1 m[label] 1 m

2m

e Zinc nitrate 1mf (e) Number mole of nitric acid = 2(50)/1000 = 0.1 mol

2 mol HNO3 1 mol Zn(NO3)2 0.1 mol HNO3 0.1/2 x 1 mol Zn(N03)2 0.05 mol Zn(NO3)2

Mass of salt = 0.05 x (65 + 2(14) + 6(16) =0.05x189 = 9.45 g

1m

1m

1m

g Zinc carbonate / zinc 1mtotal 11m

Max=10m

Suggested Answer mark5.a.i Alkenes 1ma.ii CnH2n n=2,3...... 1m b When the number of carbon atom increase the molecular weight also

increaseSo the attraction force between molecule increaseHence more energy is needed to overcome that force

1m

1m1m

c C2H4 + H2O C2H5OH

2m

No. Answers Marks 4.a) Heat change when 1 mol of water is formed from 1 mol H+ ion and 1

mol OH- ion1

b) Q - nitric acid / hydrochloric acidP – ethanoic acid

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c) nNaOH = 100 (1.0) = 0.1 1000

∆H = H ; H = ∆H x n n = 55000 x 0.1 = 5500 J

H = mcᴓ ᴓ = 5500 200(4.2) = 6.5 0C

1

1

1d) i) Heat of neutralisation in experiment II is higher than heat of

neutralisation in experiment I1

d) ii) - Some heat given out during neutralisation- Is used to dissociate the acid molecules completely

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e)

- 1- 1

∆H= - 57 kJmol-1

H20

H+ + OH-

Excess zinc oxide

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d

2m

e 1m

total 10m

6. Diagram 6 shows the apparatus set-up for an experiment to investigate electron transferat a distance in redox reactions.

(a) State the colour of acidified potassium dichromate(VI) solution.

……Orange ……………………………………………………..[l m]

(b) When the circuit is completed, the galvanometer shows a deflection.

(i) Write the half-equation for the reaction at X.

2I- I2 + 2e ……[l m]

(ii) State the type of reaction in 6(b)(i).

………oxidation …………………………….……[l m]

(iii) Describe briefly a chemical test to identify the product formed in 6(b)(i).

………Add starch solution to the product formed Dark blue solution is formed OR Add 1,1,1 trichloroethane solution Purple colour at the lower layer formed……. [2 m]

(c) (i) The half-equation below shows the reaction that occurs in acidified potassium dichromate(Vl) solution. Complete the half-equation.

n

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Cr2O72- + …14. H+ + …6.. e → 2 Cr3+ + …7. H2O

[2m](ii) Based on the answers in 6(b)(i) and 6(c)(i), on Diagram 6, draw the arrows

to show the direction of electron flow. [1m]

d. to allow the movement of ion to complete the circuit ………………………….1m

e. Ferum (II) sulphate …………………………………………………..1m

MARKING SCHEME FOR ESSAY

Answer Marks

8 Suggested metal : Zinc and magnesium

The ions present in the green solution are Fe2+ and ( H+ and OH- from

water )

The change in oxidation number of Fe is from +3 to +2

Fe3+ undergoes reduction reaction

The change in oxidation number of Mg is from 0 to +2

Mg undergoes oxidation reaction

Fe3+ acts as oxidizing agents because oxidizes Mg to Mg2+

Mg as reducing agents because reduces Fe3+ to Fe2+

Half equation (oxidation) Mg Mg2+ + 2e

Half-equation (Reduction) Fe3+ + e Fe2+

1

1

1

1

1

1

1

1

1

1

Max Mark : 10

PAPER 3 ANSWER SCHEME

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Question Mark Scheme Marks

22

7 (a) Able to record the burette readings accurately and write the volume of gas correctlyAnswer:

Set 1 25.50 24.50Set 2 20.00 30.00

3

Able to record the burette readings accurately and write the volume of gas correctlyAnswer:

90 25.50 24.50120 20.0 30.0

Or90 25.5 24.5120 20.0 30.0

Or90 25.5 24.5120 20. 30.

2

Able to record at least one burette reading less accuratelySample answer:25.5// 22

1

No response or wrong response 0Question Mark Scheme Marks

7 (b) Able to state the change of volume of gas evolved accuratelySample answer:The volume of gas increases until (210 seconds/ 32.0 cm3/ remain/ maximum/ constant/ final volume)

3

Able to state the change of volume of gas evolved less accuratelySample answer:The volume of gas increases.

2

Able to give an idea on the change of volume of gas evolved Sample answer:The volume of gas change.r: remain only

1

No response or wrong response 0

Question Mark Scheme Marks

7 (c) Able to state all the variables correctlySample answer:Manipulated variable: size of marble chips/ total surface area of marble chipsResponding variable: rate of reaction/ volume of gas per unit time Constant variable: hydrochloric acid, marble chips, mass of marble chips, temperature of acid, volume and concentration of hydrochloric acid (any correct two)

3

Able to state all the variables less correctlySample answer:Manipulated variable: marble chips

2

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Responding variable: volume of gasconstant variable: hydrochloric acid, marble chips, mass of marble chips, temperature of acid, volume and concentration of hydrochloric acid (any correct two)Able to give idea for all the variablesSample answer:Manipulated variable: marble chipsResponding variable: volume of gas Constant variable: hydrochloric acid

1

No response or wrong response 0

Question Mark Scheme Marks7(d) Able to state the operational definition rate of reaction correctly

Sample answer:Volume of gas over/per time/second// rate = volume of gas evolved/time takena: volume of gas in one second.* [Formula form]Note:Volume of gas in minute score 2Volume of gas in 30 seconds score 2Volume of gas in every 30s score 1Volume of gas at 30s score 1

3

Able to state the operational definition rate of reaction less correctlySample answer:Volume of gas per minutes/ hours // 32/210// time taken for certain volume of gas collected// volume of gas evolved in fixed time.a: change/ increase of volume of gas against time.a: change of reactants/ products over time (more than idea)

2

Able to give an idea of operational definition of the rate of reactionSample answer:The change/ increase/ decrease in the amount of [products]/[reactants]// [time taken]a: rate of [products]/ [reactants] produce.a: any products / reactants.

1

No response or wrong response 0